1. Field of the Invention
The present invention relates to a method of fitting of a hearing aid.
2. Prior Art
Before a hearing aid user starts using his or her hearing aid, or hearing aids if he needs two, the hearing aid must be fitted to suit the hearing deficiency of the hearing aid user. Normally, this fitting takes place in an interactive session between the hearing aid user and a fitter, typically an audiologist, at the audiologist's clinic.
During the session, the audiologist attempts to determine the users hearing deficiency and adjusts the adjustable parameters in the hearing aid to fit the determined deficiency. The hearing aid as such relies on so many adjustable parameters that it will be an impossible task for anyone, even the skilled audiologist, to adjust them all. Instead, a fitting software accompanying each product family is used in conjunction with a computer and possibly a control box for fitting the hearing aid.
In this respect, a central functionality incorporated in modern hearing aids is an amplitude compression of the microphone signal that can account for the degradation in the compression performed in the auditory system of a hearing impaired person. The compression can be varied over the frequency range in accordance with the person's hearing loss. Also, the effective compression ratio can be varied with signal magnitude within a limited frequency band.
As a specific example of the reduced parameter set, the fitting software does not allow an audiologist to freely set the compression curves. Instead, simpler fitting rules are used such that basic compression curves are selected in accordance with a few simple measurements on the hearing impaired person. An example is an audiogram, which specifies the hearing threshold over frequency. Subsequently, this basic setting can be fine-tuned, e.g. based on how the person with hearing impairment perceives the amplification at soft sounds or loud sounds or whether there appears to be a noticeable problem with the mutual balance between the hearing aids, if he has two (binaural fitting).
One problem relating to the hearing aid fitting is that in this interactive session it can be quite challenging—even for a highly skilled audiologist—to immediately make a perfect hearing aid fitting. Sound perception is very subjective, and also it may take quite a while to get used to the sound of a new hearing aid. In addition to this, the fitting situation is typically quite different from the environment that the user is usually subject to. Thus, if the initial fitting made by the audiologist is not appropriate, this may not become evident until the user has become accustomed to his or her new hearing aid or new set of hearing aids by trying them for a longer period of time in familiar situations.